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TSA Statement regarding the Greenpeace document, "This Vinyl House"
We have carefully reviewed the document, "This Vinyl House," published by Greenpeace. In it, the group claims that vinyl products expose children to dangerous chemicals. This is not true. Vinyl (or PVC) has been used in products for decades without any evidence of harm to human health.
In particular, throughout the document, the authors suggest that the presence of tin stabilizers in plastic products poses a danger to consumers. This, also, is not true. We are taking this opportunity to set the record straight.
The authors' arguments are based on two incorrect assumptions:
1) The authors incorrectly assume that the presence of a substance in a vinyl compound means there is exposure to that substance when the vinyl product is used. This is not true. Presence does not necessarily mean exposure; exposure must be measured separately.
2) The authors incorrectly suggest that all organotin compounds are alike. Based on this incorrect suggestion, the authors confuse one type of organotin compound that is never used as an additive in vinyl products with organotin compounds that are used as additives in vinyl and other plastics. These various organotin compounds are formulated to provide completely different properties. They are never used interchangeably.
Tin stabilizers are part of a broad class of compounds called organotins, so named because they contain at least one bond between tin and carbon. There are distinct differences among the various types of organotins, specifically between the tri-alkyl-tin compounds (three tin-carbon bonds) and the mono- (one tin-carbon bond) and di- (two tin-carbon bonds) alkyl-tin compounds.
The mono- and di-alkyl tins are used as additives that improve the
properties of various types of plastics. Their primary uses are:
§ as stabilizers in some vinyl plastics, to prevent compounds from
degrading when exposed to high heat during processing; and
§ as catalysts in certain polyurethane, polyester and silicone
systems to speed up chemical reactions.
They also are used in glass coating applications.
Trialkyltins, on the other hand, have biocidal properties - that is, they can destroy harmful organisms. (Herbicides, for example, have biocidal properties.) In particular, the trialkyltins mentioned in the article - tributyltins (TBTs) - are never used as stabilizers, but rather as anti-foulants in marine paints. Paints containing TBT are applied to the portion of a ship's hull below the waterline to discourage marine animals and plants that would otherwise adhere to it.
Greenpeace is incorrectly applying the characteristics of TBT compounds to all organotin compounds when, in fact, tin stabilizers do not have biocidal properties. Calling for a ban on the use of all organotins because TBT has biocidal properties is a bit like banning all mushrooms because some mushrooms are poisonous.
Greenpeace tested consumer products and claimed to have found trace amounts of tributyltin in some of the products. While TBT is never used as a stabilizer in vinyl, trace amounts can sometimes be detected due to chemical impurities in certain stabilizers. However, these trace amounts - typically in parts per billion or parts per trillion - do not pose a risk to human health because they are enclosed in the polymer - thus no exposure - and they are in such minute quantities as to pose no risk. (To put this in perspective, one part per billion is roughly equivalent to one drop of ink in one of the largest tanker trucks used to haul gasoline.)
It is important to note that study after study has failed to find any evidence that tins used as stabilizers in vinyl products pose a health risk for consumers who use them. They have been safely used in vinyl products for more than 50 years and there is absolutely no credible evidence of harm. In fact, regulatory agencies like the U.S. Food and Drug Administration (FDA) and others throughout the world have approved the use of certain tin stabilizers in critical applications like food wrap and pipes that carry drinking water.
The important issue for consumers is whether there is any potential health risk involved in using vinyl products. The appropriate use of tin stabilizers does not pose any such risk. Consumers can continue to use these products with confidence.
December 7, 2001
